The technology of palm print identification has been widely used in the past several decades, as features of a palm print have high stability and are not easily affected by changes in environment or physiology. At present, a kind of main palm print identification method is CCD optical image extraction method, in which four processes of a CCD image acquisition, a feature extraction for palm print, a storage of feature data and a comparison and matching of eigenvalues are performed to complete an identification. Based on the principle of total reflection of light, the method acquires an image of a palm print and extracts image information by using a CCD. Then, a clear palm print image is obtained after information processes such as filtering and image enhancing. The clear palm print image is then converted into feature data, thereby feature information is obtained.
However, this method requires a CCD device to transmit optical information, which has a large volume and high power consumption. Moreover, the palm print image used therein is easily to be duplicated and the method cannot distinguish a living body and a non-living body, thus its safety is poor.
On the other hand, the most important feature of a palm print is line feature, and the clearest lines among line features are basically invariable during one's whole life, and can be clearly identified in a case of low resolution. Thus, by using capacitive identification data as a combination of line features, point features, texture features and geometric features of a palm, one's identity can be completely confirmed.